An ischemic stroke -- the most common type -- is caused by blocked blood flow to the brain.

The study "highlights the need for more focused research, improved stroke prevention and possibly different treatment strategies for Asian-Americans," said study author Dr. Sarah Song. She's an assistant professor of cerebrovascular disease at Rush University Medical Center in Chicago.

Song and her colleagues analyzed the outcomes of more than 1.7 million ischemic stroke patients treated at more than 2,100 U.S. hospitals between 2004 and 2016. About 4 percent were Asian-American.

Along with increased risk of severe stroke and poorer outcomes, Asian-American patients were less likely to receive the clot-busting drug tissue plasminogen activator (tPA). This drug improves the chances of recovering from a stroke.

Asian-Americans also had more serious and bleeding complications when given tPA, even if they received it quickly, and had poorer functional recovery, according to the study.

The researchers did find that stroke care for both Asian-Americans and whites has improved over time.

"Looking from 2004 to 2016, our study shows that overall, patients with acute ischemic stroke are recovering more, and they are receiving more IV tPA, with less complications and better post-stroke care," Song said.

"This likely has to do with an overall improvement in stroke quality and highly effective stroke systems of care," she said.

The results were scheduled for presentation Friday at the American Stroke Association's International Stroke Conference, in Los Angeles.

However, Asian-Americans and whites had nuanced differences over time, Song pointed out. "For example, only whites had a decrease in trend in stroke severity, while Asian-Americans had a greater increase in timely IV tPA administration," she said in an association news release.

Song said stroke and stroke care among Asian-Americans has received limited attention.

"Among Asian-Americans, the various minority populations differ in so many ways," she noted. "Vietnamese people are not the same as Korean, who are not the same as Japanese or South Asian groups. Aside from differences in language, differences in stroke risk factors, diet and lifestyle, and other cultural factors, make compiling all Asian-American groups into one single group problematic."

Research presented at meetings is usually considered preliminary until published in a peer-reviewed medical journal.